The present invention relates generally to coordinate measuring machines, and more particularly to using coordinate measuring machine probe center data to determine airfoil characteristics.
Airfoils are used typically in aircraft engine blades and vanes, and generally have highly sculptured complex surface geometries which must be manufactured to meet precise engineering characteristics. The tolerances on the characteristics are tightly specified in order to meet performance requirements. The outside shape of the airfoil can be determined by manually inspecting the airfoil with a hard gauge such as a guillotine gauge. However, the hard gauge is very subjective and the results vary from one user to another. Another approach in determining the outside shape of the airfoil is to analyze probe center points taken on a section-by-section basis from a coordinate measuring machine (CMM). The CMM approach is computationally intensive and is highly dependent upon accurate, ordered and well distributed probe touch points. Typically, manual methods such as graphically or textually deleting the offending points from the electronic file are used to eliminate errant CMM data and to order the points in a consistent orientation about the airfoil on a section-by-section basis. Planar touch point correction of the CMM probe touch points and subsequent airfoil characteristics are determined by using continuous geometry and curve-fitting approximation methods that make assumptions about the distribution of the CMM probe center data, nominal and actual airfoil shapes. As mentioned above, this method is computationally intensive and is highly dependent upon accurate, ordered and well distributed probe touch points, which is not very practical for a typical CMM.